Peptides that specifically target tumor and tumor associated microenvironments, such as the tumor vasculature, after their systematic delivery, are called “tumor-specific internalizing peptides” (TSIPs) or “tumor homing peptides” (THPs).
Similar to anti-cancer peptides, tumor-specific internalizing or tumor homing peptides are usually short peptides in sequence lengths of 3 to 15 amino acids that specifically recognize and bind to tumor cells or tumor vasculature.
Tumor homing peptides have common sequence motifs such as the amino acid sequences RGD, or NGR. These peptide motifs specifically bind to a surface molecule on tumor cells or tumor vasculature.
The best known examples are the short peptides RGD and NGR.
- The RGD (Arg-Gly-Asp) peptide is known to bind α integrins.
- The NGR (Asn-Gly-Arg) peptide is known to bind to a receptor aminopeptidase N present on the surface of tumor endothelial cells, also called tumor angiogenic markers.